This invention relates to a private cellular system, as a wireless office system. More particularly, the invention relates to a method for establishing and updating a neighbor cell list used by mobile stations of the private system for cell selection.
A mobile station (MS), in accordance with one aspect of ANSI-136rev.A, stores in memory PSP/POF (Public Service Profiles/Private Operating Frequencies) identities. The PSP/POF identities are used by the MS, when camped on a public digital control channel (DCCH) to find and connect automatically with a private system. The MS searches for a POF (the frequency of the DCCH of the private system) when it is camped on a public DCCH which it determines to be a stored PSP. This avoids an undesirable manual search by the MS user.
A digital wireless office system (DWOS) is a private mobile communication system that provides an extension to mobile stations in many office environments. Mobile cellular phones used in DWOS are capable of roaming between the DWOS and a public cellular system which has one or more cells in the area, sometimes referred to herein as neighbor cells or public neighbor cells. A roaming mobile station requires information regarding the Digital Control Channels (DCCH) of the neighbor cells. The PSPs stored in an MS should represent the public neighbor cells most likely for the MS to camp on when outside of DWOS. The method described herein develops information concerning the control channels of neighbor cells which information is then transmitted to and stored in the mobile stations.
The method disclosed herein establishes and updates the neighbor cell list of a DWOS. The neighbor cell list is used by MSs to update their PSP/POF lists.
More particularly, one feature of the method is that the DWOS scans transmissions from the neighbor cell base stations, identifies digital control channels from the scanned transmissions and selects the most relevant of the identified control channels for the list. The list is then transmitted to the DWOS mobile stations.
Another feature of the method is that identified control channels are validated; and those that are invalid are discarded.
A further feature is that the most relevant control channels are selected on the basis of the received signal strength.
Yet another feature is that the list is based on more than one scan and selection to avoid changes in the list for temporary or transient control channel conditions.
Still another feature of the method is that where public systems operate on two or more bands an attempt is made to identify and list at least one channel per band.
A further feature is where the public system mobile stations have special information for cell selection (e.g. do not camp on a competitor""s network), this information is incorporated in the criteria for establishing the list of neighbor cells.
Other features and advantages of the invention will be apparent from the following description and from the drawings.